Qink

The xcolor plugin is an easy-to-use jQuery extension to manipulate colors in all imaginable combinations. This plugin implements an extensiv color parser and a featureful set of color-manipulation methods. There is also an animate() extension to smooth CSS colors.

Another useful method isReadable() completes the whole, by allowing you to check if a text is readable on a certain background. The color value can also be passed in different color models: RGB, HSV/HSB, HSL and their adequate alpha extensions.